1. Field of the Invention
The present invention relates to a spring seat of a suspension for an automotive vehicle, which is provided between a coil spring and an opposed member for reduces transmission vibrations between the coil spring and the opposed member, the opposed member being one member selected from a body member and a support member for a wheel.
2. Description of Related Art
As shown on pages 5 through 6 of “Vibration-Isolating • Shock-Absorbing Device (the last volume)”, The collected mechanism diagrams published by The Japan society of Mechanical Engineers on Sep. 10, 1977, in one example of the conventional spring seat of a suspension for an automotive vehicle, the spring seat has been composed of only a cylindrical elastic rubber body. This spring seat has non-through holes which are formed in a cylindrical member from the side of the opposed member toward the side of the coil spring. These non-through holes are formed in a circumferential direction of the cylindrical member.
And, recently, in order to improve the stiffness of the spring seat, the spring seat including a core member composed of metal or resin in addition to the elastic rubber body has been proposed (see JP-A-2002-130351). With this arrangement, the spring characteristics can be made soft by virtue of the elastic rubber body, and the stiffness of the entire spring seat can be improved by virtue of the core member.
Recently, in order to respond to the demand for the reduction of production costs, it has been considered to compose the spring seat of only the elastic rubber body without using any core member.
The elastic rubber body of the spring seat disclosed in the above-described publication has radially extending cutouts in a surface on the side of the opposed member, and accordingly, the elastic rubber body has radially extending projections on the side of the opposed member. Where the spring seat including only the elastic rubber body thus arranged without including any core member is interposed between the coil spring and the opposed member, and is pressed therewith, the radially extending projections may be deformed into buckling configurations.
When the radially extending projections are deformed into buckling configurations, the relative positions of the coil spring and the spring seat may be offset from each other. In this case, the center axis located at a spring center of the coil spring may be offset from the axial center of the spring seat, namely so-called misalignment of centers may occur. As a result, the coil spring may come off the spring seat, and consequently, the spring seat may become impossible to support the coil spring so as not to properly perform the function of reducing transmission vibrations.
In addition, deformed projections are exposed in an outer peripheral surface of the spring seat so that the appearance quality of the spring seat is degraded.
To solve these problems, it can be considered to form such non-through holes as disclosed in the above-described collected mechanism diagrams without forming radially extending cutouts in the elastic rubber body. Indeed, by forming the non-through holes, the buckling deformations of the spring seat can be prevented. Therefore, the misalignment of centers of the spring seat as well as the degradation of the appearance quality thereof can be prevented.
On the other hand, with the spring seat disclosed in the above described collected mechanism diagrams, internal spaces defined with the non-through holes provided in the spring seal perform compression and return motions as the coil spring expands and contracts when an automotive vehicle is running, for example. An entire surface of the spring seat, which is on the side of the opposed member, contacts the opposed member. And openings of the non-through holes provided in the spring seat are located on the side of the opposed member. Namely, the internal spaces of the non-through holes define closed spaces depending on the deformed state of the elastic rubber body. Consequently, when the non-through holes return from the compressed state, for example, the internal spaces of the non-through holes become partially open from the closed state so that noises may occur.